1. Field of the Invention
The present invention relates to control systems for remotely controlled model airplanes and, more particularly, to magnetically operated centrally biased control surfaces for a model airplane.
2. Description of Related Prior Art
Remotely controlled, and formerly referred to as radio controlled, model airplanes have been built and flown as a hobby since the 1940s when vacuum tube operated transmitters and receivers became available for use in model airplanes. With advances in the transmitter/receiver art, there have been significant size and weight reductions in the related equipment and there have been significant improvements in reducing the electrical power requirements. With such reductions in size and weight, smaller and lighter model airplanes became possible to be remotely controlled.
Initially, the control system actuated by a signal from the receiver was a rubber band driven escapement that provided left or right rudder deflection for directional control. Generally, such escapements lacked sufficient power to deflect the elevator to obtain a change in pitch or to deflect the ailerons to obtain a left or right rolling moment about the longitudinal axis. Moreover, control of the engine speed and operation was primarily limited to shutting down the engine, which engine was usually a single cylinder internal combustion engine. As technology advanced, several servo mechanisms were developed which had significant power to operate the various control surfaces and to provide a throttling capability for the engine. During the last ten years or so, the size of these servos has been significantly reduced. They also became capable of full proportional control to accurately deflect the respective control surface(s).
Through careful aerodynamic design of a model airplane, it is possible to control not only the direction of flight but also the pitch attitude of a model airplane using only deflection of the rudder. A skilled pilot can even do basic aerobatic maneuvers using only selected timed rudder deflection. For small sized lightweight model airplanes, a magnetic actuator for the rudder was available a number of years ago. This actuator included a coil to drive a linkage connected to the rudder of the model airplane. The signal transmitted by the transmitter and received by the receiver either energized the coil or de-energized the coil. The rudder was biased in one direction during the absence of a signal and upon transmission of a control signal, the coil was energized to cause deflection of the rudder in the other direction. By regulating the relative on/off periods of energizing the coil, directional control of the airplane could be maintained but a great deal of skill by the ground based pilot was required. Because of the low power output of the coil, the linkage connected to the rudder had to be very carefully adjusted, be essentially slop free and minimal friction was required.
With the advent of micro sized receivers, electric motors and small powerful batteries, small and light weight model airplanes can now be remotely controlled. As small and light weight model airplanes require relatively small forces to actuate control surfaces for controlling movement in the pitch, yaw and longitudinal axis, new and innovative low power servo mechanisms can be used for these purposes.